Coverting from 2wd to 4wd Questions

[DesertBurb88]

I recently purchased a 1988 Chevy 3/4 Ton, 454, TH400, 2wd, 8 lug Suburban. Its a great vehicle, runs great 97% complete just got some minor issues that need to be repaired or replaced. Only thing missing from this massive workhorse was 4wd.

Recently a very good friend of mine who ownes a 1989 GMC 3/4 Ton, 350, 700R4, 4wd , 8 lug Suburban decided after buying a 2014 Dodge 3500 4x4 dually with cummings and allison trans, he was not going to be no-opping his suburban again and gave it too me for a doner vehicle if I wanted to swap 4x4 drive train over.

Now to the point. The 4x4 is a complete suburban it runs and drives but (in fact the first suburban that I ever drove 8 years ago that made me want one of these trucks). It has a bent frame my buddy knows this cause he had the accident 20+ years ago and knows the frame was straightened as much as possible but is still bent causing the vehicle to lean. (I don't need reasons or cures to fix this problem as we both know its non repairable without a new frame).

My question is this with me having a complete running 2wd and a complete running 4wd what how hard would it be to convert my 2wd to 4wd. Will all the suspension and drivetrain (less the 350) come over to my vehicle and bolt on. Or am I looking at alot of custom modding to get the parts to bolt up.

Depending on the answers I hear from people on here I might just be taking the parts I need from the 4wd and parting out the rest. The condition to me getting the truck was that he got to keep the 350 as he (mechanic) has a client that he can sell the engine too.

[crashz]

I'm not positive that 2wd frame are the same as 4wd frames, but i think they are. You have the the best possible situation, as you have the same model, same year (basically) of vehicles to do this swap. The donor is complete and running, so you really could not be in a better position.

It's a fair amount of work, as you'll be removing the entire front and rear axle assemblies of each vehicle, removing the spring mounts and bolting them to your frame. I may be mistaken, but I believe you need to swap out the rear spring mounts as well, to keep the 4wd ride height. Little things like brake lines and cables will be time consuming.

If the donor's frame is bent, be sure to replace any bent suspension components. If budget allows, new springs would be best. The springs would have had 20 years to acclimate to the bent frame.

Other than the engine, I would not give anything away on the donor until you are done.

[DesertBurb88]

Thanks for the only response so far. I appreciate the imput.

[STREET BLAZIN]

Nooooooo, your doing it all wrong.....
It's harder to scrape the ground with a 4WD.
Gosh.
Well if that's what you need to do, then ok.
All of what crashz said sounds dead on.
The spring hangers are longer on the 4X, and everything should cary over to the new frame.
You may have to swap the floor pan to make room for the transfer case.
I know how easy these frames bend, when I stripped my blazer frame down, the frame rails just wobbled around like a noodle.
Make sure the frame brase in front of the engine and where the steer box mounts is good and rigid or it will walk all over the road.
Bigger tires will make it worse, I welded a strait frame brase in place of the old curved one.

[DesertBurb88]

Thanks for the input speaking with my buddy thats the mechanic he said I would probably also have to have a drive shaft made

[BaggedRanger]

speaking from going from a factory 2wd frame and buying a 4wd because my 2wd was hit and whoever had it before me did a half arse job on trying to fix it so I bought a straight 4wd frame..

The front should just swap right out. Everything to go from control arms to leafs are there. You just need to bolt it up. The shackles on the rear of the 4wd are longer than a 2wd. The e-brake cable is routed differently on a 4wd versus a 2wd.. Why I have no idea but it is different. I think there are a few other things I am forgetting but all in all you should be able to swap stuff out on it.

One thing I would highly recommend if it isn't done already since you are going to go 4wd with it is to box in the front part of the frame where the steering box mounts to. If it isn't broke by now it will break eventually..

[crashz]

Originally Posted by DesertBurb88

Thanks for the input speaking with my buddy thats the mechanic he said I would probably also have to have a drive shaft made

If you are swapping all the drivetrain over, then no, you'll use the 4wd drive shafts.

[DesertBurb88]

Crashz thats what I thought too. But he seemed insistent on the matter. And yeah only issue I could see is drivetrain will be bolting up to a 454 instead of the 350 in the donor truck. Which might cause one of the driveshafts to be to long or short depending.

Street Blazin: I'm not opposed to dropping my ride just using the update front clip and misc other parts from the donor and parting out the rest on here for others, leaving it 2 wd and down close to the ground but no one has came up with any suggestions for lowering without bagging it, and where I live there are too many dirt roads that don't handle bags well.

[crashz]

I've heard of that before, but i have my doubts. I once swapped the 6.2L diesel with a 454 in my 83, and had no issues with the motor mount/transmission location. But that was not a small block. Should be easy to measure though. Measure the distance between the bellhousing and motor mount on the big block and small block. Personally, I can't see much of a variation here, otherwise the engine would either be placed into the firewall or far way from it.

[DesertBurb88]

Crashz thanks for the input and it almost have to be a slight variance between engines on these trucks.

[cheepin]

The drive shafts will work just fine. There is no issue going from a SBC to a BBC. The motor mount to bell housing distance is the same. I have put a 454 in place of a SB 400 in a 79 suburban. I didn't move the transmission cross member. Did the opposite in my CJ/buggy.
It will be a bit of work. You will need to pull the complete front 2wd assembly off. Which means a lot of time grinding and cutting the factory rivets. The 2wd cross member needs to be swapped to either the 4wd cross member or an aftermarket one. Yes the rear spring hangers are taller on the 4x4 but I would just save that extra work and put a short lift block in to get the height leveled out.